Encapsulated semiconductor nanocrystals formed in insulators by ion beam synthesis

White, C. W.; Budai, J. D.; Withrow, S. P.; Zhu, Jane G.; Sonder, E.; Zuhr, R. A.; Meldrum, A.; Hembree, D. M.; Henderson, D. O.; Prawer, Steven

doi:10.1016/s0168-583x(98)00091-3

Cited by 119 publications

(45 citation statements)

References 42 publications

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“…Nanocrystals of CdS dispersed in dielectric matrices have been produced using several techniques such as melting [1], sol-gel [2], Langmuir-Blodgett [3], colloidal solution [4], deposition from the vapour phase [5], ion-implantation [6] and, more recently, in nanoporous anodised alumina films [7]. Usually the as-prepared films are amorphous at room temperature and the formation and growth of the CdS nanocrystals is induced by post-annealing for various temperatures and times.…”

Section: Introductionmentioning

confidence: 99%

“…Usually the as-prepared films are amorphous at room temperature and the formation and growth of the CdS nanocrystals is induced by post-annealing for various temperatures and times. The size of the nanocrystals is controlled by the annealing conditions and this procedure normally requires high temperatures and several hours of operation, leading to a broad distribution of nanocrystal sizes inside the matrix [1][2][3]5,6,8]. For anodised alumina films, the nanocrystal size is imposed by the pore dimension, typically 10 nm, and for films produced by ion-beam synthesis the nanocrystals are above 20 nm, i.e.…”

Section: Introductionmentioning

confidence: 99%

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HRTEM and GIXRD studies of CdS nanocrystals embedded in Al2O3 films produced by magnetron RF-sputtering

Conde

Rolo

Gomes

et al. 2003

Journal of Crystal Growth

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In this paper we report on the structural properties of as-grown CdS nanoparticles embedded in Al 2 O 3 films produced by a magnetron RF-sputtering technique. Grazing incidence X-ray diffraction together with high-resolution transmission electron microscopy (HRTEM) and electron diffraction were used to study the crystallinity and morphology of the CdS nanocrystals. Depending on the deposition parameters, elongated or spherical nanocrystals were grown. HRTEM shows evidence of the growth of CdS nanocrystals at room temperature with sizes in the range of 3-8 nm, and indicates that the nanocrystals formed in the cubic phase during the early stages of the deposition process. Stress-free films were formed under selected deposition conditions. r

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

HRTEM and GIXRD studies of CdS nanocrystals embedded in Al2O3 films produced by magnetron RF-sputtering

Conde

Rolo

Gomes

et al. 2003

Journal of Crystal Growth

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“…In order to study the material properties of nanoclusters, it can be useful to embed nanoclusters in stable and inert ceramics such as MgO, which can be achieved by ion implantation and subsequent annealing. 13 It is expected that the wide-band-gap material MgO ͑7.8 eV͒ does not interact with the electronic structure of metal and semiconductor clusters. 14,7 It is also optically transparent in a large frequency band, which facilitates optical studies.…”

Section: Introductionmentioning

confidence: 99%

Positron confinement in embedded lithium nanoclusters

et al. 2002

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Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgOʈLi interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

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“…In this work 10ϫ10ϫ1 mm 3 epipolished single crystals of MgO͑100͒ and MgO͑110͒ implanted with (1 ϫ10 16 )-cm Ϫ2 30-keV 6 Li ions and postannealed to 950 K for 30 min were used for the depth-selective positron experiments. The depth-selective 2D-ACAR measurements were carried out using an Anger-camera-type setup coupled with POSH, the high-intensity monoenergetic positron beam with a flux of 8ϫ10 7 e ϩ /s.…”

Section: Methodsmentioning

confidence: 99%

“…4,5 Nanoclusters embedded in inert matrices are usually produced by ion implantation and subsequent annealing. 6,7 Their size can be influenced by the selection of the type of matrix, the ion implantation fluence and energy, and the time and temperature of the annealing stage. Consequently, one can modify the electronic and optical properties of the matrix in which the nanoclusters are embedded.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and orientation relationship of Li nanoclusters embedded in MgO studied by depth-selective positron annihilation two-dimensional angular correlation

et al. 2002

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Quantum-confined positrons are sensitive probes for determining the electronic structure of nanoclusters embedded in materials. In this work, a depth-selective positron annihilation 2D-ACAR ͑two-dimensional angular correlation of annihilation radiation͒ method is used to determine the electronic structure of Li nanoclusters formed by implantation of 10 16 -cm Ϫ2 30-keV 6 Li ions in MgO ͑100͒ and ͑110͒ crystals and by subsequent annealing at 950 K. Owing to the difference between the positron affinities of lithium and MgO, the Li nanoclusters act as quantum dots for positrons. 2D-ACAR distributions for different projections reveal a semicoherent fitting of the embedded metallic Li nanoclusters to the host MgO lattice. Ab initio KorringaKohn-Rostoker calculations of the momentum density show that the anisotropies of the experimental distributions are consistent with an fcc crystal structure of the Li nanoclusters. The observed reduction of the width of the experimental 2D-ACAR distribution is attributed to positron trapping in vacancies associated with Li clusters. This work proposes a method for studying the electronic structure of metallic quantum dots embedded in an insulating material.

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Encapsulated semiconductor nanocrystals formed in insulators by ion beam synthesis

Cited by 119 publications

References 42 publications

HRTEM and GIXRD studies of CdS nanocrystals embedded in Al2O3 films produced by magnetron RF-sputtering

HRTEM and GIXRD studies of CdS nanocrystals embedded in Al2O3 films produced by magnetron RF-sputtering

Positron confinement in embedded lithium nanoclusters

Electronic structure and orientation relationship of Li nanoclusters embedded in MgO studied by depth-selective positron annihilation two-dimensional angular correlation

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